Despite the well-recognized cognitive deficits in Neurofibromatosis type 1 (NF1), the mechanisms underlying the neuropathophysiology remain unclear. The clear lack of translation from findings in mouse models to the clinic manifests the inherent species differences in the development, architecture and function of rodent and human brains, and underscores the urgent need to develop and use human model systems to study aspects of human brain disorders and to bridge the translational gap to the clinic. Our long-term goal is to develop and use human cellular models to elucidate the molecular and cellular mechanisms underlying the cognitive deficits associated with NF1. Recent advances in the field of epigenetic reprogramming, stem cell biology and genetic engineering has rendered us a unique opportunity to model neurodevelopmental disorders such as NF1 in a manner that is highly complementary to murine transgenic approaches by that maintains fidelity with complex human cellular contexts. The objective of the current study is to harness such tools to characterize the abnormalities in neurodevelopment and neuronal network activity caused by NF1-associated mutations and determine the cellular and molecular mechanisms underlying Neurofibromin 1 (NF1 encoding protein) - regulated biological processes in different cellular contexts. Based on the preliminary data produced in the applicant?s laboratory, we hypothesize that disease associated mutations in NF1 affect proliferation and cell fate commitment of human neural progenitor cells that control neuronal output; and impair neuronal network activity through a potentially human-specific mechanism. The hypothesis will be tested using two complementary cellular models: 1) human brain organoids will be used to investigate the role of Neurofibromin 1 in human neural progenitor cell types, especially the outer radial glial cells that are largely absent in the rodent developing cortices. A multidisciplinary approach will be used to characterize cell type-specific defects in neuroepithelial cell expansion, migration, differentiation, and the mitotic properties of cells; 2) induced neuronal (iN) system, which was developed by the applicant and others, will be used to dissect the cellular mechanisms underlying the irregular neuronal network activity observed in cultures consisting of NF1 mutant neurons. The current study would be the first systematic investigation of Neurofibromin 1 completion of the proposed project function in the neural system using a human model system. Successful will provide novel knowledge on the role of Neurofibromin 1 in different neural cell types that are relevant to the pathophysiology of NF1. Given the high prevalence of Autism in NF1, the proposed research also has the potential to shed light on the key molecular and cellular mechanisms underlying idiopathic Autism.